This invention generally relates to apparatus and method for forming a fibrous article. The fibrous article can be a fibrous web, and the fibrous web may be employed to produce absorbent pads for applications such as disposable diapers, child""s training pants, feminine care articles, incontinence articles, and the like.
In the general practice of forming fibrous web materials, such as laid fibrous articles, it has been common to utilize a fibrous sheet of cellulosic or other suitable absorbent material which has been fiberized in a conventional fiberizer, or other shredding or comminuting device, to form discrete fibers. In addition, particles of superabsorbent material have been mixed with the fibers. The fibers and superabsorbent particles have then been entrained in an air stream and directed to a foraminous forming surface upon which the fibers and superabsorbent particles have been deposited to form an absorbent fibrous web. Typically the formed fibrous web has provided an interconnected plurality of appointed, fibrous pads. The fibrous web has been cut or otherwise segmented to provide individual pads. During the manufacturing operations, the scarfing operation has been employed to provide multiple functions. For example, the scarfing operation has been employed to level the peaks and valleys off the top of the formed fibrous web so that, from pad to pad along the length of the fibrous web, each pad can have substantially the same basis weight of absorbent material. Additionally, the scarfing operation has been employed to help control and regulate the desired basis weight distributions within each individual pad.
Adjustments to the basis weight distributions have, for example, been made by providing a foraminous forming surface that has predetermined depressions or pocket regions that allow an accumulation of relatively large amounts of absorbent material. Additionally, the location and configuration of the scarfing roll has been selectively adjusted. For example, by reducing the effective gap between the scarfing roll and the forming surface, the scarfing roll can be arranged to remove more material from the fibrous web. The amounts of removed material have been recirculated through the forming process, and have been employed to help fill the deeper pocket regions of the forming surface. The filling of the pocket regions has been accomplished by an over-forming of the pad with the selected absorbent material, and a mechanical redistribution of the absorbent material.
The prior practice of forming airlaid fibrous webs has employed various scarfing mechanisms to produce desired distributions of basis weight along the formed fibrous webs. For example, the scarfing mechanisms have been employed to produce gradations of basis weight along a longitudinal direction of the formed web, i.e., in the direction of movement of the fibrous web through the forming process or apparatus. Conventional scarfing mechanisms have also been employed for providing basis weight variations along a transverse, cross-direction of the formed web.
For example, particular scarfing systems have employed scarfing rolls that have been configured to provide a timed scarfing of the fibrous web. In other systems, a web conveyor is moved towards and away from the scarfing roll to generate changes in basis-weight distribution. Further systems have employed multiple scarfing rolls, or have employed a reverse venting airflow.
Absorbent pads in desired consumer products are, however, being constructed with relatively large differences in the amount of absorbent material placed in different sections of the pad. For example, larger amounts of absorbent fiber and superabsorbent particles are being placed in the appointed front portions of the pad, and much smaller amounts of absorbent fiber and superabsorbent particles are being placed in the appointed back portions of the pad. As a result, a basis-weight profile can be generated across the length and/or width of the pads, and the profiles can include large changes in basis-weight. The manufacture of such pads with high-variation, basis-weight profiles has required the scarfing of larger amounts of material at higher scarfing rates. Conventional scarfing systems, however, have not adequately provided the higher levels of scarfing mass-flow needed to produce the desired pads. Conventional scarfing systems, such as those described above, have experienced various difficulties. One difficulty has been an increased re-circulation of fibers from the scarfing housing back into the forming chamber. This situation can make it difficult to maintain a desired basis weight in the fibrous web. Another difficulty has been a plugging or jamming of the fibrous web as it leaves the forming chamber or as the fibrous web enters the scarfing housing. This situation can develop during transient situations, such as during a sequence of shutting down and starting up the web forming operation. In a further difficulty, the fibrous material that has been scarfed and removed from the fibrous web may not be adequately discharged from the scarfing housing. As a result, an accumulation of fibrous material may jam or otherwise degrade the scarfing operation. For example, fibrous material may accumulate within the scarfing housing and, at random intervals, break free to redeposit onto the fibrous web. The relatively unpredictable redeposit of fibrous material can generate excessive variations in the basis weight of the fibrous web. Where the fibrous web also includes particulate material, such as particles of superabsorbent material, the particulate material removed from the web may not be adequately directed out of the discharge conduit, and may accumulate within the scarfing housing, or may undesirably exit out from other openings in the scarfing housing. As a result, there has been a continuing need for improved scarfing systems that can more reliably produce and maintain the desired distributions of basis weight along the scarfed web.
The present invention provides a distinctive method and apparatus for scarfing a fibrous web. The technique of the invention can include a scarfing housing which has been provided with a web entrance portion, a web exit portion, a discharge conduit, and an air flow inlet. A rotatable scarfing roll can be located in the scarfing housing, and the discharge conduit can be configured with a selected conduit angle. In a particular aspect, the discharge conduit can be configured with a conduit angle of not more than about 80 degrees.
In another aspect, the method and apparatus of the invention can include a movable damper which is operatively positioned in the web entrance portion of the scarfing housing, and is capable of changing a size of an entrance opening in the web entrance portion of the scarfing housing. In a further aspect, the method and apparatus of the invention can include an inlet chimney portion which is configured to provide a selected stripper air flow towards the scarfing roll. In still another aspect, the method and apparatus can include at least one insert member which is configured to operatively impede a movement of particulate material removed from the fibrous web during the scarfing of the fibrous web.
In its various aspects and features, the method and apparatus of the present invention can more effectively help to provide an improved technique for scarfing fibrous webs. The invention can provide a distinctive scarfing system which can exhibit a higher scarfing capacity, a decreased plugging tendency, and a reduced variability in the desired basis weight distributions that are intended for production along and across the scarfed web.